What Is Fluconazole Used For ? My Dad Is Experiencing

What is fluconazole used for ?
My dad is experiencing severe abdominal pain and severe nausea. He can not eat. He is forcing V8 juice (4oz) and Ensure (4oz.) because he knows that he has to have some nourishment. He was treated successfully for shingles and pneumonia since Thanksgiving. He entered the hospital 3 weeks ago yesterday. Had an endoscopy and colonoscopy plus barium swallow. Biopsies were taken while inside digestive track, only results were yeast infection found at base of esophagus. He has current medications of flaconanole, pantoprazole , bicalutamide, and Percocet for pain as needed and phenargan for nausea. After 2 weeks of treatment for digestive issues, we see no improvement. Can you help us think through this to suggest another type of treatment